The present invention relates to a master slice integrated circuit which contains arrays of logic cells that can be connected to perform various functions.
As shown in FIG. 1, a prior art master slice integrated circuit comprises clock distributors 5 and flip-flops 4 which are arranged on cells of linear cell arrays together with circuits 10 of other logic functions on a chip substrate 1 and the cell arrays are separated by regions 6 which contain wire patterns for interconnecting between cells. Clock pulses of different repetition frequencies and phases are supplied from clock distributor cells 5 to associated flip-flop cells 4 over separate clock wires 7 which extend across the wire pattern regions 6. The cells on each linear cell array are composed of general purpose, discrete random logic circuits, or gates which are used as basic building blocks to create desired logic functions. The flip-flop cells are typically constructed according to the logic array TTL/SSI 9000 Specifications. According to the logic array specifications, each flip-flop is made up of twelve logic gates and each logic gate is usually composed of five transistors. Each flip-flop thus contains as many as 60 transistors.
Since the general tendency is toward high operating speeds and high level of performance and sophistication, circuit designers have directed their efforts to increasing circuit packing density and minimizing the length of interconnecting wires. With the prior art logic gate technique, the locations of the flip-flop and clock distributor cells depend largely on the locations of the associated logic cells of particular logic functions, and therefore it is almost impossible to shorten the length of the clock wires as desired even though automatic placement programs may be used. From the view points of packing density and clock propagation time, the prior art master slice integrated circuits are not satisfactory, and improvements have been desired.